<!DOCTYPE html><html><head>

    <!-- responsive -->
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width,initial-scale=1,maximum-scale=1,user-scalable=no">
    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
    <meta name="HandheldFriendly" content="true">


<meta charset="utf-8"><style>body {
  width: 45em;
  border: 1px solid #ddd;
  outline: 1300px solid #fff;
  margin: 16px auto;
}

body .markdown-body
{
  padding: 30px;
}

@font-face {
  font-family: fontawesome-mini;
  src: url(data:font/woff;charset=utf-8;base64,d09GRgABAAAAAAzUABAAAAAAFNgAAQAAAAAAAAAAAAAAAAAAAAAAAAAAAABGRlRNAAABbAAAABwAAAAcZMzaOEdERUYAAAGIAAAAHQAAACAAOQAET1MvMgAAAagAAAA+AAAAYHqhde9jbWFwAAAB6AAAAFIAAAFa4azkLWN2dCAAAAI8AAAAKAAAACgFgwioZnBnbQAAAmQAAAGxAAACZVO0L6dnYXNwAAAEGAAAAAgAAAAIAAAAEGdseWYAAAQgAAAFDgAACMz7eroHaGVhZAAACTAAAAAwAAAANgWEOEloaGVhAAAJYAAAAB0AAAAkDGEGa2htdHgAAAmAAAAAEwAAADBEgAAQbG9jYQAACZQAAAAaAAAAGgsICJBtYXhwAAAJsAAAACAAAAAgASgBD25hbWUAAAnQAAACZwAABOD4no+3cG9zdAAADDgAAABsAAAAmF+yXM9wcmVwAAAMpAAAAC4AAAAusPIrFAAAAAEAAAAAyYlvMQAAAADLVHQgAAAAAM/u9uZ4nGNgZGBg4ANiCQYQYGJgBEJuIGYB8xgABMMAPgAAAHicY2Bm42OcwMDKwMLSw2LMwMDQBqGZihmiwHycoKCyqJjB4YPDh4NsDP+BfNb3DIuAFCOSEgUGRgAKDgt4AAB4nGNgYGBmgGAZBkYGEAgB8hjBfBYGCyDNxcDBwMTA9MHhQ9SHrA8H//9nYACyQyFs/sP86/kX8HtB9UIBIxsDXICRCUgwMaACRoZhDwA3fxKSAAAAAAHyAHABJQB/AIEAdAFGAOsBIwC/ALgAxACGAGYAugBNACcA/wCIeJxdUbtOW0EQ3Q0PA4HE2CA52hSzmZDGe6EFCcTVjWJkO4XlCGk3cpGLcQEfQIFEDdqvGaChpEibBiEXSHxCPiESM2uIojQ7O7NzzpkzS8qRqnfpa89T5ySQwt0GzTb9Tki1swD3pOvrjYy0gwdabGb0ynX7/gsGm9GUO2oA5T1vKQ8ZTTuBWrSn/tH8Cob7/B/zOxi0NNP01DoJ6SEE5ptxS4PvGc26yw/6gtXhYjAwpJim4i4/plL+tzTnasuwtZHRvIMzEfnJNEBTa20Emv7UIdXzcRRLkMumsTaYmLL+JBPBhcl0VVO1zPjawV2ys+hggyrNgQfYw1Z5DB4ODyYU0rckyiwNEfZiq8QIEZMcCjnl3Mn+pED5SBLGvElKO+OGtQbGkdfAoDZPs/88m01tbx3C+FkcwXe/GUs6+MiG2hgRYjtiKYAJREJGVfmGGs+9LAbkUvvPQJSA5fGPf50ItO7YRDyXtXUOMVYIen7b3PLLirtWuc6LQndvqmqo0inN+17OvscDnh4Lw0FjwZvP+/5Kgfo8LK40aA4EQ3o3ev+iteqIq7wXPrIn07+xWgAAAAABAAH//wAPeJyFlctvG1UUh+/12DPN1B7P3JnYjj2Ox4/MuDHxJH5N3UdaEUQLqBIkfQQioJWQ6AMEQkIqsPGCPwA1otuWSmTBhjtps2ADWbJg3EpIXbGouqSbCraJw7kzNo2dRN1cnXN1ZvT7zuuiMEI7ncizyA0URofRBJpCdbQuIFShYY+GZRrxMDVtih5TwQPHtXDFFSIKoWIbuREBjLH27Ny4MsbVx+uOJThavebgVrNRLAiYx06rXsvhxLgWx9xpfHdrs/ekc2Pl2cpPCVEITQpwbj8VQhfXSq2m+Wxqaq2D73Kne5e3NjHqQNj3CRYlJlgUl/jRNP+2Gs2pNYRQiOnmUaQDqm30KqKiTTWPWjboxnTWpvgxjXo0KrtZXAHt7hwIz0YVcj88JnKlJKi3NPAwLyDwZudSmJSMMJFDYaOkaol6XtESx3Gt1VTytdZJ3DCLeaVhVnCBH1fycHTxFXwPX+l2e3d6H/TufGGmMTLTnbSJUdo00zuBswMO/nl3YLeL/wnu9/limCuD3vC54h5NBVz6Li414AI8Vx3iiosKcQXUbrvhFFiYb++HN4DaF4XzFW0fIN4XDWJ3a3XQoq9V8WiyRmdsatV9xUcHims1JloH0YUa090G3Tro3mC6c01f+YwCPquINr1PTaCP6rVTOOmf0GE2dBc7zWIhji3/5MchSuBHgDbU99RMWt3YUNMZMJmx92YP6NsHx/5/M1yvInpnkIOM3Z8fA3JQ2lW1RFC1KaBPDFXNAHYYvGy73aYZZZ3HifbeuiVZCpwA3oQBs0wGPYJbJfg60xrKEbKiNtTe1adwrpBRwlAuQ3q3VRaX0QmQ9a49BTSCuF1MLfQ6+tinOubRBZuWPNoMevGMT+V41KitO1is3D/tpMcq1JHZqDHGs8DoYGDkxJgKjHROeTCmhZvzPm9pod+ltKm4PN7Dyvvldlpsg8D+4AUJZ3F/JBstZz7cbFRxsaAGV6yX/dkcycWf8eS3QlQea+YLjdm3yrOnrhFpUyKVvFE4lpv4bO3Svx/6F/4xmiDu/RT5iI++lko18mY1oX+5UGKR6kmVjM/Zb76yfHtxy+h/SyQ0lLdpdKy/lWB6szatetQJ8nZ80A2Qt6ift6gJeavU3BO4gtxs/KCtNPVibCtYCWY3SIlSBPKXZALXiIR9oZeJ1AuMyxLpHIy/yO7vSiSE+kZvk0ihJ30HgHfzZtEMmvV58x6dtqns0XTAW7Vdm4HJ04OCp/crOO7rd9SGxQAE/mVA9xRN+kVSMRFF6S9JFGUtthkjBA5tFCWc2l4V43Ex9GmUP3SI37Jjmir9KqlaDJ4S4JB3vuM/jzyH1+8MuoZ+QGzfnvPoJb96cZlWjMcKLfgDwB7E634JTY+asjsPzS5CiVnEWY+KsrsIN5rn3mAPjqmQBxGjcGKB9f9ZxY3mYC2L85CJ2FXIxKKyHk+dg0FHbuEc7D5NzWUX32WxFcWNGRAbvwSx0RmIXVDuYySafluQBmzA/ssqJAMLnli+WIC90Gw4lm85wcp0qjArEDPJJV/sSx4P9ungTpgMw5gVC1XO4uULq0s3v1rqLi0vX/z65vlH50f8T/RHmSPTk5xxWBWOluMT6WiOy+tdvWxlV/XQb3o3c6Ssr+r6I708GsX9/nzp1tKFh0s3v7m4vAy/Hnb/KMOvc1wump6Il48K6mGDy02X9Yd65pa+nQIjk76lWxCkG8NBCP0HQS9IpAAAeJxjYGRgYGBhcCrq214Qz2/zlUGenQEEzr/77oug/zewFbB+AHI5GJhAogBwKQ0qeJxjYGRgYH3/P46BgZ0BBNgKGBgZUAEPAE/7At0AAAB4nGNngAB2IGYjhBsYBAAIYADVAAAAAAAAAAAAAFwAyAEeAaACCgKmAx4DggRmAAAAAQAAAAwAagAEAAAAAAACAAEAAgAWAAABAAChAAAAAHiclZI7bxQxFIWPd/JkUYQChEhIyAVKgdBMskm1QkKrRETpQiLRUczueB/K7HhlOxttg8LvoKPgP9DxFxANDR0tHRWi4NjrPIBEgh1p/dm+vufcawNYFWsQmP6e4jSyQB2fI9cwj++RE9wTjyPP4LYoI89iWbyLPIe6+Bh5Hs9rryMv4GbtW+RF3EhuRa7jbrIbeQkPkjdUETOLnL0Kip4FVvAhco1RXyMnSPEz8gzWxE7kWTwUp5HnsCLeR57HW/El8gJWa58iL+JO7UfkOh4l9yMv4UnyEtvQGGECgwF66MNBooF1bGCL1ELB/TYU+ZBRlvsKQ44Se6jQ4a7hef+fh72Crv25kp+8lNWGmeKoOI5jJLb1aGIGvb6TjfWNLdkqdFvJw4l1amjlXtXRZqRN7lSRylZZyhBqpVFWmTEXgWfUrpi/hZOQXdOd4rKuXOtEWT3k5IArPRzTUU5tHKjecZkTpnVbNOnt6jzN8240GD4xtikvZW56043rPMg/dS+dlOceXoR+WPbJ55Dsekq1lJpnypsMUsYOdCW30o103Ytu/lvh+5RWFLfBjm9/N8hJntPhvx92rnoE/kyHdGasGy754kw36vsVf/lFeBi+0COu+cfgQr42G3CRpeLoZ53gmfe3X6rcKt5oVxnptHR9JS8ehVUd5wvvahN2uqxOOpMXapibI5k7Zwbt4xBSaTfoKBufhAnO/uqNcfK8OTs0OQ6l7JIqFjDhYj5WcjevCnI/1DDiI8j4ndWb/5YzDZWh79yomWXeXj7Nnw70/2TIeFPTrlSh89k1ObOSRVZWZfgF0r/zJQB4nG2JUQuCQBCEd07TTg36fb2IyBaLd3vWaUh/vmSJnvpgmG8YcmS8X3Shf3R7QA4OBUocUKHGER5NNbOOEvwc1txnuWkTRb/aPjimJ5vXabI+3VfOiyS15UWvyezM2xiGOPyuMohOH8O8JiO4Af+FsAGNAEuwCFBYsQEBjlmxRgYrWCGwEFlLsBRSWCGwgFkdsAYrXFhZsBQrAAA=) format('woff');
}

@font-face {
  font-family: octicons-anchor;
  src: url(data:font/woff;charset=utf-8;base64,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) format('woff');
}

.markdown-body {
  font-family: sans-serif;
  -ms-text-size-adjust: 100%;
  -webkit-text-size-adjust: 100%;
  color: #333333;
  overflow: hidden;
  font-family: "Helvetica Neue", Helvetica, "Segoe UI", Arial, freesans, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  word-wrap: break-word;
}

.markdown-body a {
  background: transparent;
}

.markdown-body a:active,
.markdown-body a:hover {
  outline: 0;
}

.markdown-body b,
.markdown-body strong {
  font-weight: bold;
}

.markdown-body mark {
  background: #ff0;
  color: #000;
  font-style: italic;
  font-weight: bold;
}

.markdown-body sub,
.markdown-body sup {
  font-size: 75%;
  line-height: 0;
  position: relative;
  vertical-align: baseline;
}
.markdown-body sup {
  top: -0.5em;
}
.markdown-body sub {
  bottom: -0.25em;
}

.markdown-body h1 {
  font-size: 2em;
  margin: 0.67em 0;
}

.markdown-body img {
  border: 0;
}

.markdown-body hr {
  -moz-box-sizing: content-box;
  box-sizing: content-box;
  height: 0;
}

.markdown-body pre {
  overflow: auto;
}

.markdown-body code,
.markdown-body kbd,
.markdown-body pre,
.markdown-body samp {
  font-family: monospace, monospace;
  font-size: 1em;
}

.markdown-body input {
  color: inherit;
  font: inherit;
  margin: 0;
}

.markdown-body html input[disabled] {
  cursor: default;
}

.markdown-body input {
  line-height: normal;
}

.markdown-body input[type="checkbox"] {
  box-sizing: border-box;
  padding: 0;
}

.markdown-body table {
  border-collapse: collapse;
  border-spacing: 0;
}

.markdown-body td,
.markdown-body th {
  padding: 0;
}

.markdown-body .codehilitetable {
  border: 0;
  border-spacing: 0;
}

.markdown-body .codehilitetable tr {
  border: 0;
}

.markdown-body .codehilitetable pre,
.markdown-body .codehilitetable div.codehilite {
  margin: 0;
}

.markdown-body .linenos,
.markdown-body .code,
.markdown-body .codehilitetable td {
  border: 0;
  padding: 0;
}

.markdown-body td:not(.linenos) .linenodiv {
  padding: 0 !important;
}

.markdown-body .code {
  width: 100%;
}

.markdown-body .linenos div pre,
.markdown-body .linenodiv pre,
.markdown-body .linenodiv {
  border: 0;
  -webkit-border-radius: 0;
  -moz-border-radius: 0;
  border-radius: 0;
  -webkit-border-top-left-radius: 3px;
  -webkit-border-bottom-left-radius: 3px;
  -moz-border-radius-topleft: 3px;
  -moz-border-radius-bottomleft: 3px;
  border-top-left-radius: 3px;
  border-bottom-left-radius: 3px;
}

.markdown-body .code div pre,
.markdown-body .code div {
  border: 0;
  -webkit-border-radius: 0;
  -moz-border-radius: 0;
  border-radius: 0;
  -webkit-border-top-right-radius: 3px;
  -webkit-border-bottom-right-radius: 3px;
  -moz-border-radius-topright: 3px;
  -moz-border-radius-bottomright: 3px;
  border-top-right-radius: 3px;
  border-bottom-right-radius: 3px;
}

.markdown-body * {
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}

.markdown-body input {
  font: 13px Helvetica, arial, freesans, clean, sans-serif, "Segoe UI Emoji", "Segoe UI Symbol";
  line-height: 1.4;
}

.markdown-body a {
  color: #4183c4;
  text-decoration: none;
}

.markdown-body a:hover,
.markdown-body a:focus,
.markdown-body a:active {
  text-decoration: underline;
}

.markdown-body hr {
  height: 0;
  margin: 15px 0;
  overflow: hidden;
  background: transparent;
  border: 0;
  border-bottom: 1px solid #ddd;
}

.markdown-body hr:before,
.markdown-body hr:after {
  display: table;
  content: " ";
}

.markdown-body hr:after {
  clear: both;
}

.markdown-body h1,
.markdown-body h2,
.markdown-body h3,
.markdown-body h4,
.markdown-body h5,
.markdown-body h6 {
  margin-top: 15px;
  margin-bottom: 15px;
  line-height: 1.1;
}

.markdown-body h1 {
  font-size: 30px;
}

.markdown-body h2 {
  font-size: 21px;
}

.markdown-body h3 {
  font-size: 16px;
}

.markdown-body h4 {
  font-size: 14px;
}

.markdown-body h5 {
  font-size: 12px;
}

.markdown-body h6 {
  font-size: 11px;
}

.markdown-body blockquote {
  margin: 0;
}

.markdown-body ul,
.markdown-body ol {
  padding: 0;
  margin-top: 0;
  margin-bottom: 0;
}

.markdown-body ol ol,
.markdown-body ul ol {
  list-style-type: lower-roman;
}

.markdown-body ul ul ol,
.markdown-body ul ol ol,
.markdown-body ol ul ol,
.markdown-body ol ol ol {
  list-style-type: lower-alpha;
}

.markdown-body dd {
  margin-left: 0;
}

.markdown-body code,
.markdown-body pre,
.markdown-body samp {
  font-family: Consolas, "Liberation Mono", Menlo, Courier, monospace;
  font-size: 12px;
}

.markdown-body pre {
  margin-top: 0;
  margin-bottom: 0;
}

.markdown-body kbd {
  background-color: #e7e7e7;
  background-image: -moz-linear-gradient(#fefefe, #e7e7e7);
  background-image: -webkit-linear-gradient(#fefefe, #e7e7e7);
  background-image: linear-gradient(#fefefe, #e7e7e7);
  background-repeat: repeat-x;
  border-radius: 2px;
  border: 1px solid #cfcfcf;
  color: #000;
  padding: 3px 5px;
  line-height: 10px;
  font: 11px Consolas, "Liberation Mono", Menlo, Courier, monospace;
  display: inline-block;
}

.markdown-body>*:first-child {
  margin-top: 0 !important;
}

.markdown-body>*:last-child {
  margin-bottom: 0 !important;
}

.markdown-body .headeranchor-link {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  display: block;
  padding-right: 6px;
  padding-left: 30px;
  margin-left: -30px;
}

.markdown-body .headeranchor-link:focus {
  outline: none;
}

.markdown-body h1,
.markdown-body h2,
.markdown-body h3,
.markdown-body h4,
.markdown-body h5,
.markdown-body h6 {
  position: relative;
  margin-top: 1em;
  margin-bottom: 16px;
  font-weight: bold;
  line-height: 1.4;
}

.markdown-body h1 .headeranchor,
.markdown-body h2 .headeranchor,
.markdown-body h3 .headeranchor,
.markdown-body h4 .headeranchor,
.markdown-body h5 .headeranchor,
.markdown-body h6 .headeranchor {
  display: none;
  color: #000;
  vertical-align: middle;
}

.markdown-body h1:hover .headeranchor-link,
.markdown-body h2:hover .headeranchor-link,
.markdown-body h3:hover .headeranchor-link,
.markdown-body h4:hover .headeranchor-link,
.markdown-body h5:hover .headeranchor-link,
.markdown-body h6:hover .headeranchor-link {
  height: 1em;
  padding-left: 8px;
  margin-left: -30px;
  line-height: 1;
  text-decoration: none;
}

.markdown-body h1:hover .headeranchor-link .headeranchor,
.markdown-body h2:hover .headeranchor-link .headeranchor,
.markdown-body h3:hover .headeranchor-link .headeranchor,
.markdown-body h4:hover .headeranchor-link .headeranchor,
.markdown-body h5:hover .headeranchor-link .headeranchor,
.markdown-body h6:hover .headeranchor-link .headeranchor {
  display: inline-block;
}

.markdown-body h1 {
  padding-bottom: 0.3em;
  font-size: 2.25em;
  line-height: 1.2;
  border-bottom: 1px solid #eee;
}

.markdown-body h2 {
  padding-bottom: 0.3em;
  font-size: 1.75em;
  line-height: 1.225;
  border-bottom: 1px solid #eee;
}

.markdown-body h3 {
  font-size: 1.5em;
  line-height: 1.43;
}

.markdown-body h4 {
  font-size: 1.25em;
}

.markdown-body h5 {
  font-size: 1em;
}

.markdown-body h6 {
  font-size: 1em;
  color: #777;
}

.markdown-body p,
.markdown-body blockquote,
.markdown-body ul,
.markdown-body ol,
.markdown-body dl,
.markdown-body table,
.markdown-body pre,
.markdown-body .admonition {
  margin-top: 0;
  margin-bottom: 16px;
}

.markdown-body hr {
  height: 4px;
  padding: 0;
  margin: 16px 0;
  background-color: #e7e7e7;
  border: 0 none;
}

.markdown-body ul,
.markdown-body ol {
  padding-left: 2em;
}

.markdown-body ul ul,
.markdown-body ul ol,
.markdown-body ol ol,
.markdown-body ol ul {
  margin-top: 0;
  margin-bottom: 0;
}

.markdown-body li>p {
  margin-top: 16px;
}

.markdown-body dl {
  padding: 0;
}

.markdown-body dl dt {
  padding: 0;
  margin-top: 16px;
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</style><title>stm32-vpc</title></head><body><article class="markdown-body"><h1 id="vpc-stm32"><a name="user-content-vpc-stm32" href="#vpc-stm32" class="headeranchor-link" aria-hidden="true"><span class="headeranchor"></span></a>移植 VPC 到 STM32 平台</h1>
<blockquote>
<p>VCP 是虚拟串口（ Virtual COM Port Driver）的简称。通过它可以种将 USB 抽象当做串口使用，使主控端的实现非常简单，但是速度又是 USB 的速度。</p>
</blockquote>
<div class="toc">
<ul>
<li><a href="#vpc-stm32">移植 VPC 到 STM32 平台</a><ul>
<li><a href="#_1">环境搭建</a></li>
<li><a href="#_2">新建工程</a></li>
<li><a href="#_3">移植代码</a></li>
<li><a href="#_4">枚举分析</a></li>
</ul>
</li>
</ul>
</div>
<h2 id="_1"><a name="user-content-_1" href="#_1" class="headeranchor-link" aria-hidden="true"><span class="headeranchor"></span></a>环境搭建</h2>
<p>硬件平台</p>
<ul>
<li><a href="http://www.st.com/web/en/resource/technical/document/datasheet/CD00191185.pdf">STM32F10x</a></li>
<li><a href="http://www2.keil.com/mdk5/ulink">ULINK2</a></li>
</ul>
<p>软件平台</p>
<ul>
<li><a href="http://www.keil.com/arm/mdk.asp">Keil MDK 4.70</a></li>
<li><a href="http://www.stmcu.org/document/detail/index/id-214187">PC端虚拟串口驱动 1.3.1</a></li>
</ul>
<p>库版本</p>
<ul>
<li><a href="http://www.st.com/web/en/catalog/tools/PF258157">STM32_USB-FS-Device_Lib_V4.0.0</a></li>
<li><a href="https://my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Flat.aspx?RootFolder=%2fpublic%2fSTe2ecommunities%2fmcu%2fLists%2fcortex_mx_stm32%2fSTM32%20Legacy%20Firmware%20Libraries&amp;FolderCTID=0x01200200770978C69A1141439FE559EB459D7580009C4E14902C3CDE46A77F0FFD06506F5B&amp;TopicsView=https%3A%2F%2Fmy%2Est%2Ecom%2Fpublic%2FSTe2ecommunities%2Fmcu%2FLists%2Fcortex_mx_stm32%2FAllItems%2Easpx&amp;currentviews=11077">STM32F10x_StdPeriph_Lib_V3.5.0</a></li>
</ul>
<p>问题：</p>
<ul>
<li>枚举主要做哪些事情？<blockquote>
<p>When the Host powers up it polls each of the Slave devices in turn (using the reserved address 0), it assigns each one a unique address and finds out from each device what its Speed is and the and type of data transfer it wishes to perform. This process is called <strong>enumeration</strong> and it also takes place whenever a device is plugged into an active network. <br />
(<a href="http://www.computer-solutions.co.uk/info/Embedded_tutorials/usb_tutorial.htm">http://www.computer-solutions.co.uk/info/Embedded_tutorials/usb_tutorial.htm</a>)</p>
</blockquote>
</li>
<li>为什么USB每隔1ms就进一次中断，如 STM32 的<code>USB_LP_CAN1_RX0_IRQHandler</code>中断函数？<blockquote>
<p>he SOF packet consisting of an 11-bit frame number is sent by the host every 1ms ±  500ns on a full speed bus or every 125 µs ±  0.0625 µs on a high speed bus.<br />
(<a href="http://www.beyondlogic.org/usbnutshell/usb3.shtml">http://www.beyondlogic.org/usbnutshell/usb3.shtml</a>)</p>
</blockquote>
</li>
<li>主控轮询从设备的时间是如何确定的？</li>
<li>在bulk传输方式中，如果传输的数据长度小于最大传输长度，需要用零补充么？会发生什么呢？<blockquote>
<p>If the data payload falls short of the maximum packet size, it doesn&rsquo;t need to be padded with zeros. A bulk transfer is considered complete when it has transferred the exact amount of data requested, transferred a packet less than the maximum endpoint size, or transferred a zero-length packet.<br />
(<a href="http://www.beyondlogic.org/usbnutshell/usb4.shtml">http://www.beyondlogic.org/usbnutshell/usb4.shtml</a>)</p>
</blockquote>
</li>
<li>什么是pipe？什么是Endpoint？</li>
<li>如何确定使用哪个EndPoint？以及如何更改EP？</li>
<li>数据是什么时候写入Buffer？</li>
<li>写入Buffer之后，啥时候发出去？</li>
<li>为什么不管是PC还是STM32都需要在发完数据之后，再发送个全零帧？</li>
<li>为什么每次的数据大小是 64 字节？可以更改么？</li>
<li>USB 2.0 Full Speed的最快速度是多少？</li>
<li>为什么调试器的断点不是调试USB的好方法？<blockquote>
<p>These timeout periods are quite acceptable for even the slowest of devices, but can be a restriction during debugging. 50mS doesn&rsquo;t provide for many debugging characters to be sent at 9600bps on an asynchronous serial port or for a In Circuit Debugger/Emulator to single step or to break execution to examine the internal Registers. As a result, USB requires some different debugging methods to that of other microcontroller projects.<br />
<a href="http://www.beyondlogic.org/usbnutshell/usb6.shtml">http://www.beyondlogic.org/usbnutshell/usb6.shtml</a></p>
</blockquote>
</li>
</ul>
<p>参考：</p>
<ul>
<li><a href="https://github.com/mintisan/mintisan.github.io/wiki/USB">usb wiki</a></li>
</ul>
<h2 id="_2"><a name="user-content-_2" href="#_2" class="headeranchor-link" aria-hidden="true"><span class="headeranchor"></span></a>新建工程</h2>
<p>新建本地文件夹目录结构：</p>
<ul>
<li>将<code>STM32F10x_StdPeriph_Lib_V3.5.0</code>的<code>Libraries</code>中的所有文件放到<code>BSP</code>下；</li>
<li>将 <code>STM32_USB-FS-Device_Lib_V4.0.0</code>库中的<code>Libraries\STM32_USB-FS-Device_Driver</code>中的所有文件放到<code>USBLib</code>下；</li>
<li>将 <code>STM32_USB-FS-Device_Lib_V4.0.0</code>库中的<code>Projects\Virtual_COM_Port\src</code>所有文件放到<code>USER</code>下；</li>
<li>新建<code>LISTING</code>用于存放临时生成的链接文件；</li>
<li>新建<code>OUTPUT</code>用于存放最终生成的BIN和HEX文件。</li>
</ul>
<p>最终本地目录树如下：</p>
<pre><code>├─BSP                     //STM32F10x_StdPeriph_Lib_V3.5.0/Libraries
│  ├─CMSIS
│  │  ├─CM3
│  │  │  ├─CoreSupport
│  │  │  └─DeviceSupport
│  │  │      └─ST
│  │  │          └─STM32F10x
│  │  │              └─startup
│  │  │                  ├─arm
│  │  │                  ├─gcc_ride7
│  │  │                  ├─iar
│  │  │                  └─TrueSTUDIO
│  │  └─Documentation
│  └─STM32F10x_StdPeriph_Driver
│      ├─inc
│      └─src
├─LISTING                                  //lst文件
├─OUTPUT                          //输出文件，如BIN或者HEX
├─USBLib                          //STM32_USB-FS-Device_Lib_V4.0.0/Libraries
│  ├─inc
│  └─src
└─USER                //STM32_USB-FS-Device_Lib_V4.0.0\Projects\Virtual_COM_Port
    ├─inc
    └─src
</code></pre>

<p>在<code>USER</code>根目录新建工程</p>
<p><img alt="打开MDK，Create New Project" src="http://mint-blog.qiniudn.com/stm32-vpc-1.png" /></p>
<p>选择芯片</p>
<p><img alt="STM32F103RC" src="http://mint-blog.qiniudn.com/stm32-vpc-2.png" /></p>
<p>无需将启动文件添加工程，稍后手动添加，以防止版本不对</p>
<p><img alt="startup_stm32f10x_hd.s" src="http://mint-blog.qiniudn.com/stm32-vpc-3.png" /></p>
<p>右键工程名，组织工程的目录结构，将工程目录与本地一一对应</p>
<p><img alt="Components, Enviroment and Books" src="http://mint-blog.qiniudn.com/stm32-vpc-4.png" /></p>
<p>最终工程目录树</p>
<p><img alt="Project Tree" src="http://mint-blog.qiniudn.com/stm32-vpc-5.png" /></p>
<p>点击<code>小魔术棒</code>设置<code>Output</code></p>
<p><img alt="Options for Output" src="http://mint-blog.qiniudn.com/stm32-vpc-6.png" /></p>
<p>设置<code>Listings</code></p>
<p><img alt="Options for Listings" src="http://mint-blog.qiniudn.com/stm32-vpc-7.png" /></p>
<p>设置预处理宏和头文件路径，还有一定要加上<code>--c99</code>这样就可以随处定义变量了！！！</p>
<p><img alt="Options for C/C++ Header" src="http://mint-blog.qiniudn.com/stm32-vpc-8.png" /></p>
<p><img alt="Options for C/C++" src="http://mint-blog.qiniudn.com/stm32-vpc-9.png" /></p>
<p>选择调试器和设置Flash的大小，勾选<code>Reset and Run</code>，这样每次下载完程序便可以自动运行，而不是手动复位一次再运行</p>
<p><img alt="Flash Download" src="http://mint-blog.qiniudn.com/stm32-vpc-a.png" /></p>
<h2 id="_3"><a name="user-content-_3" href="#_3" class="headeranchor-link" aria-hidden="true"><span class="headeranchor"></span></a>移植代码</h2>
<p>在之前，放在<code>USER</code>中的代码要么与平台相关，要么是可以修改的配置文件，需要针对特定情况进行修改。</p>
<p>先删除掉一些不需要的文件，由于目前针对STM32F1平台，故可以将F2，F3和L1平台的文件删除，如<del>stm32f30x_conf.h，stm32l1xx_conf.h ，stm32f37x_conf.h ，system_stm32f30x.c，system_stm32l1xx.c  ， system_stm32f37x.c </del>。</p>
<p>删除完之后剩下如下文件，大致可以分成 USB 配置相关和平台硬件相关</p>
<p><strong>平台硬件相关</strong></p>
<ul>
<li>platform_config.h  ：USB控制引脚USB_DISCONNECT定义处</li>
<li>stm32f10x_conf.h  ：STM32 库文件模块开关，无需修改</li>
<li>hw_config.h / hw_config.c：USB引脚定义初始化和NVIC设定</li>
<li>stm32_it.h / stm32_it.c：打开USB中断<code>USB_LP_CAN1_RX0_IRQHandler</code>即可</li>
<li>main.c ：工程入口，初始化USB，无需修改</li>
</ul>
<p><strong>USB 配置相关</strong></p>
<ul>
<li>usb_conf.h：端点和对应回调函数选择处</li>
<li>usb_desc.h / usb_desc.c ：设别描述符定义，无需修改</li>
<li>usb_prop.h / usb_prop.c：过程正真执行的函数，注释掉USART相关即可</li>
<li>usb_istr.h  / usb_istr.c：在中断的执行实体<code>USB_Istr</code>函数，无需修改</li>
<li>usb_pwr.h / usb_pwr.c：低功耗以及电源模块，需要修改<code>Suspend</code>让设备不进入睡眠</li>
<li>usb_endp.c ：端点输入（EP1）/输出（EP3）回调函数的入口</li>
</ul>
<p><strong>注</strong>：不管Host还是Device的输入和输出均是站在Host的角度描述。</p>
<p>主要工作分为4部分：定义USB 控制脚引脚 USB_DISCONNECT，删除针对原评估板的USART相关代码，关掉USB进入低功耗相关和设置发送和接收实体。</p>
<p>1.注释原评估板的USE_DISCONNECT的GPIO定义，重新定义为开发板上的，如PA10：</p>
<pre><code>#define USB_DISCONNECT                      GPIOA
#define USB_DISCONNECT_PIN                  GPIO_Pin_10
#define RCC_APB2Periph_GPIO_DISCONNECT      RCC_APB2Periph_GPIOA
</code></pre>

<p>注：每一款STM32F10x的USBDM为PA11，USBDP为PA12，CTRL为自行设定。</p>
<p>2.删除USART相关的有所有定义个调用，只要与以下函数的相关的初始化，定义和调用均注释掉</p>
<pre><code>void USART_Config_Default(void);
bool USART_Config(void);
void USB_To_USART_Send_Data(uint8_t* data_buffer, uint8_t Nb_bytes);
void USART_To_USB_Send_Data(void);
</code></pre>

<p>3.注释掉Suspend函数中的所有内容，关掉睡眠</p>
<pre><code>
</code></pre>

<p>4.在<code>EP3_OUT_Callback</code>回调接收函数中设置缓存接收数据和发送数据，以下两种方式均可以。</p>
<pre><code>static uint8_t USB_Tx_Buffer[VIRTUAL_COM_PORT_DATA_SIZE];

              /* style1 : */
//               while(GetEPTxStatus(ENDP1) != EP_TX_NAK);
//               {
//                   memset(USB_Tx_Buffer,_inc++,VIRTUAL_COM_PORT_DATA_SIZE);
//                   USB_Tx_Buffer[31] = 0xAA;
//                   USB_Tx_Buffer[VIRTUAL_COM_PORT_DATA_SIZE - 10] = 0xBB;
//                   USB_SIL_Write(EP1_IN, USB_Tx_Buffer, VIRTUAL_COM_PORT_DATA_SIZE);
//                   SetEPTxValid(ENDP1);
//               }
//
//               while(GetEPTxStatus(ENDP1) != EP_TX_NAK);
//               {
//                   USB_SIL_Write(EP1_IN, USB_Tx_Buffer, 0);
//                   SetEPTxValid(ENDP1);
//               }

            /* style2 : http://bbs.21ic.com/icview-208240-1-1.html */
            while(GetEPTxStatus(ENDP1) != EP_TX_NAK);
            {
            memset(USB_Tx_Buffer,_inc++,VIRTUAL_COM_PORT_DATA_SIZE);
            USB_Tx_Buffer[3] = 2*_inc;
            UserToPMABufferCopy(USB_Tx_Buffer, ENDP1_TXADDR, VIRTUAL_COM_PORT_DATA_SIZE);
            SetEPTxCount(ENDP1,VIRTUAL_COM_PORT_DATA_SIZE);
            SetEPTxValid(ENDP1);
            }
            // over flag
            while(GetEPTxStatus(ENDP1) != EP_TX_NAK);
            {
            SetEPTxCount(ENDP1,0);
            SetEPTxValid(ENDP1);
            }
</code></pre>

<p>以下为对接收到数据进行解析，如果第一个数据位0x03，则回复相对应的数据，完成类似echo的过程，以下是<a href="http://perisoft.net/bushound/">Bus Hound</a>的显示过程。</p>
<p><img alt="bus hound" src="http://mint-blog.qiniudn.com/stm32-vpc-b.png" /></p>
<p>注：USB会在以下三种情况下将bulk方式的数据发出：第一种是其长度小于64；另一种为发送完64长度数据之后发送一帧0长度的数据。以上为后一种。还有就是等驱动的缓冲区满，如2k的数据满了之后再发出。</p>
<h2 id="_4"><a name="user-content-_4" href="#_4" class="headeranchor-link" aria-hidden="true"><span class="headeranchor"></span></a>枚举分析</h2>
<p><a href="https://www.google.co.jp/search?q=%E5%9B%BE%E8%A7%A3USB%E6%80%BB%E7%BA%BF%E6%9E%9A%E4%B8%BE%E8%BF%87%E7%A8%8B&amp;oq=%E5%9B%BE%E8%A7%A3USB%E6%80%BB%E7%BA%BF%E6%9E%9A%E4%B8%BE%E8%BF%87%E7%A8%8B&amp;aqs=chrome..69i57&amp;sourceid=chrome&amp;es_sm=119&amp;ie=UTF-8">图解USB总线枚举过程</a></p>
<p><img alt="Paste_Image.png" src="http://mint-blog.qiniudn.com/stm32-vpc-c.png" /><br />
1. 检测到USB设备后，对USB设备复位，使设备地址变为0x0。发80 06 01 00 00 40 00命令，读取设备描述符命令，由于不知道设备描述符的长度，暂时要求返回数据长度为0x40。<br />
<img alt="Paste_Image.png" src="http://mint-blog.qiniudn.com/stm32-vpc-d.png" /><br />
2. 给这个新接上的设备分配地址。<br />
<img alt="Paste_Image.png" src="http://mint-blog.qiniudn.com/stm32-vpc-e.png" /><br />
3. 设置地址成功后，对新地址发送获取设备描述符命令，此时已经知道了它的长度，直接按这个长度即可。<br />
<img alt="Paste_Image.png" src="http://mint-blog.qiniudn.com/stm32-vpc-f.png" /><br />
4. 在得到设备描述符后，我们再发获取配置描述符命令。<br />
<img alt="Paste_Image.png" src="http://mint-blog.qiniudn.com/stm32-vpc-10.png" /><br />
5. 从上一步，我们可以得到设备支持的接口数及端点数，此时再发一次得到配置描述符命令，把数据长度改大，数据长度我们可以从wTotallLength中读取，但我们一般在这里设为0xFF。<br />
<img alt="Paste_Image.png" src="http://mint-blog.qiniudn.com/stm32-vpc-11.png" /><br />
6. 如果有字符串描述符，在这里可以发命令读取。接下来再一次发命令完整读取设备描述符和配置描述符<br />
<img alt="Paste_Image.png" src="http://mint-blog.qiniudn.com/stm32-vpc-12.png" /><br />
7. 在这里发送设置配置命令，到此，我们已经完整地得到了设备的信息。枚举过程结束。<br />
<img alt="Paste_Image.png" src="http://mint-blog.qiniudn.com/stm32-vpc-13.png" /></p></article></body></html>
